1) Technical Field
The subject invention relates to a lead-through teach handle assembly for assisting a user, such as a robot operator, in teaching a desired operating path to a robot assembly within a workspace of the robot assembly. The subject invention also relates to a method of lead-through teaching the robot assembly the desired operating path within the workspace.
2) Description of the Prior Art
Various methods of lead-through teaching and handle assemblies utilized for lead-through teaching are known in the art. As appreciated, these conventional methods and assemblies are utilized to teach a desired operating path to a robot assembly in a robot workspace. Such methods and assemblies are integral throughout industry for subsequent play-back of the desired operating path that has been taught to the robot assembly such that a tool mounted to an arm of the robot assembly can operate on a particular workpiece.
Examples of conventional lead-through teach handle assemblies are disclosed in U.S. Pat. No. 5,495,410 to Graf; U.S. Pat. No. 4,408,286 to Kikuchi et al.; and U.S. Pat. No. 4,367,532 to Crum et al. These handle assemblies are deficient for various reasons. Specifically, the handle assembly disclosed in the ""410 patent to Graf is deficient in that the handle assembly is rigidly attached, i.e., not detachably mounted, to the robot assembly. Rigid attachment of the handle assembly to the robot assembly makes the handle assembly very difficult to grasp for the operator as the operator moves the robot assembly translationally and rotationally during the method of lead-through teaching. That is, it is very difficult for operators to maintain their grasp when it is necessary to make large orientation changes with the robot assembly during the method of teaching. Rigid attachment of the handle assembly may also endanger the safety of the operator during lead-through teaching in cases where the robot assembly inadvertently malfunctions and erratically moves in a direction with excessive force while the operator is grasping the handle assembly. The assembly disclosed in this patent is further deficient in that the assembly requires a six-degree of freedom digitizing arm to teach the desired operating path to the robot assembly. As understood by those skilled in the art, assemblies incorporating six-degree of freedom digitizing aims are inconvenient and expensive.
The handle assemblies disclosed in both the ""286 patent to Kikuchi et al. and the ""532 patent to Crum et al. are deficient because, similar to that described above, these handle assemblies are also rigidly attached to the robot assembly. Consequently, as discussed above, these handle assemblies are awkward to the operator when making large orientation changes during lead-through teaching and may also endanger the safety of the operator. The assembly disclosed in the ""286 patent to Kikuchi et al. is further deficient in that the assembly requires a six-degree of freedom force sensor. As understood by those skilled in the art, six-degree of freedom force sensors are expensive.
Examples for conventional methods of lead-through teaching are disclosed in Patent Abstracts of Japan Publication Nos. 61273610 A to Yasuo et al.; 08336785 A to Hideo; and 05192885 to Keiji et al. These methods are deficient for various reasons. The method disclosed in the ""610 abstract to Yasuo et al. monitors the torque of a motor within the robot assembly to assist the operator in lead-through teaching of the robot assembly. More specifically, the method disclosed in the ""610 abstract to Yasuo utilizes the monitored motor torque and adjusts the motor to supplement movement imparted on the tool by the operator while lead-through teaching of the robot assembly. The method disclosed in this abstract is particularly deficient in that the method does not monitor motor torque to command translational or rotational movement other than at the motor. This method monitors the motor torque and only adjusts the motor in response to a specific force on a particular motor. That is, in this abstract, movement is only with respect to the external force monitored at a particular motor and there is no differentiation between translational and rotational movement. The method disclosed in the ""610 abstract to Yasuo does not consider a tool center point (TCP) and an orientation of the tool as factors for adjusting the motor. As such, with this method, robot operators have considerable difficulty in moving the robot arm while maintaining a spacial relationship between the tool and the robot workspace.
Continuing, the ""785 abstract to Hideo discloses a method of teaching a robot assembly by an indirect teaching method. In such indirect teaching methods, a teaching tool, which is utilized to apply the external force for imparting the necessary movement on the robot assembly during lead-through teaching, is disconnected from or not a part of the robot assembly. That is, the external force is not applied at the tool mounted to the robot assembly. The method disclosed in this abstract is deficient in that the operator is not directly manipulating the tool on the robot assembly to apply the external force. Instead, in this method, the operator is isolated from the tool of the robot assembly and it is generally understood throughout the art that teaching of the robot assembly is less effective.
The ""885 abstract to Keiji et al. discloses a robot assembly that includes a sensor for detecting motor torque. The sensor detects motor torque to facilitate a method of lead-through teaching of the robot assembly. The method disclosed in this abstract is deficient in that the method does not disclose more than one teach operating mode that differentiates between translational and rotational movement of the robot assembly during lead-through teaching. As such, the method of lead-through teaching is less controlled for the operator. Furthermore, it is understood that sensors and controllers utilized to interpret data detected in these types of uncontrolled methods of lead-through teaching would require more technological sophistication as well as a corresponding higher cost.
Due to the inefficiencies identified above with respect to the conventional handle assemblies and the conventional methods of lead-through teaching, it is desirable to implement a novel lead-through teach handle assembly as well as a novel method of lead-through teaching a desired operating path to a robot assembly. More specifically, it is desirable to implement a lead-through teach handle assembly that is not rigidly attached to the robot assembly such that large orientation changes of the handle assembly that result from translational and rotational movement of the robot arm during teaching can be accommodated. It is also ideal for the lead-through teach handle assembly of the subject invention to maximize the safety of the operator.
The method of lead-through teaching introduced according to the subject invention does not utilize a teaching tool that is disconnected from or not part of the robot assembly to apply the external force required to move the robot assembly. Furthermore, the method of the subject invention selects between two different teach operating modes, if necessary, to present a controlled method of lead-through teaching the desired operating path to the robot assembly. Additionally, costly six-degree of freedom force sensor are not required and therefore can be eliminated in both the teach handle assembly and the method of lead-through teaching presented in the subject invention.
A method of lead-through teaching a robot assembly and a handle assembly utilized in such a method are disclosed. The method of lead-through teaching and handle assembly of the subject invention assist a user, such as a robot operator, in teaching a desired operating path to the robot assembly within a workspace of the robot assembly. The robot assembly includes at least one robot arm having at least one mounting site. The robot assembly additionally includes a tool having a tool center point and an orientation.
The handle assembly of the subject invention includes a mounting mechanism. The mounting mechanism is adapted to be mounted to the mounting sites on the robot arm. The handle assembly further includes a handle that is supported by the mounting mechanism. The handle is adapted to provide at least one surface for the user to grasp: As such, the user can apply an external force that is required to move the arm of the robot assembly along the desired operating path.
The handle assembly of the subject invention is characterized by first and second joint members that are coupled together. More specifically, the first joint member is mounted to the handle, and the second joint member is mounted to the mounting mechanism. The first and second joint members interconnect the handle and the mounting mechanism. The first and second joint members accommodate orientation changes of the handle relative to the mounting mechanism that result from translational and rotational movement of the robot arm as the user is teaching the robot assembly the desired operating path.
As noted above, a method of lead-through teaching the desired operating path to the robot assembly is also disclosed. The method of the subject invention includes the step of applying an external force at the tool to impart movement on the robot arm. The external force causes the arm of the robot assembly to move along the desired operating path. To apply the external force in the subject invention, the operator can manipulate the lead-through teach handle, including the first and second joint members, that is mounted on the robot arm. Alternatively, without the lead-through teach handle, the operator may manually hold the tool of the robot assembly and simply lead the tool and the robot arm through the desired operating path. The imparted movement is at least one of translational movement and rotational movement. That is, the movement imparted on the robot arm is either translational movement, rotational movement, or both translational and rotational movement.
Next, the method of the subject invention estimates the external force applied at the tool and generates motion commands in response to the external force. The motion commands that are generated supplement the movement imparted on the tool in a direction of the estimated external force. Therefore, the robot operator is assisted in moving the robot arm.
The subject invention continues by selecting at least one teach operating mode. The teach operating mode is selected by the operator depending upon the desired operating path to be taught. The selected teach operating mode distinguishes between a translational operating mode and a rotational operating mode. More specifically, the translational operating m ode defines a first three-degrees of freedom and limits the movement imparted on the tool to translational movement. As such, a first spacial relationship defined between the orientation of the tool and the workspace is maintained during lead-through teaching of the robot assembly. On the other hand, the rotational operating mode defines a second three-degrees of freedom and limits the movement imparted on the tool to rotational movement. As such, a second spacial relationship defined between the tool center point and the workspace is maintained during lead-through teaching of the robot assembly.
Accordingly, the subject invention provides a lead-through teach handle assembly including first and second joint members that are coupled together and that interconnect a handle and a mounting mechanism mounted to the robot assembly such that large orientation changes of the handle assembly that result from translational and rotational movement of the robot arm during teaching are accommodated. The first and second joint members provide only three-degrees of freedom such that movement of the robot assembly is limited to no more than three-degrees of freedom, either translational movement or rotational movement, and a more cost effective force sensor, such as a three-degree of freedom force sensor, can be utilized. Furthermore, the lead-through teach handle assembly of the subject invention is detachable from the robot assembly during lead-through teaching of the robot assembly such that safety of the operator is maximized.
The subject invention also provides a method of lead-through teaching that applies an external force required to move the robot assembly at a tool mounted to the robot assembly. Also, the method provided selects between a translational and rotational teach operating mode, if necessary, to present a controlled method of lead-through teaching that limits the movement imparted on the tool, if necessary, to translational movement or rotational movement. As such, more cost effective mechanisms for sensing force, other than six-degree of freedom force sensors can be utilized.